Butadienes and chlorinated derivatives thereof



Patented Feb. 16, 1937 UNITED STATES BUTADIENES AND cnLortrNA'mn DEBIV TIVES THEREOF Irving Elkin Mnskat, Chicago, Ill., assignor to E. I. du Pont de Nemours .85 Company, Wilmington, Del., a corporation of Delaware No Drawing. Application {,uiy 14, 1934, Serial I No. 135,2 1 roamin (01. 260171) This invention relates to the preparation of organic compounds and more particularly it relates to a new method for preparing diene hydrocarbons. v

Butadiene-l,3 has been oi interest in the past due to the-possibility of its being used as a raw material for the production of synthetic rubber,

1 and considerable research experimentation has been done relative to the preparation of this hydrocarbon. Caventou Ann., 127, 348 (1863), has obtained butadiene by passing the vapors of fusel oil through a hot tube, and since then it has been found in varying amounts in the pyrogenic decompositions of numerous organic compounds. Manypotential methods for preparingfbutadiene depend upon the cracking of petroleum hydro carbons. Yields of butadiene obtained by the methods referred to have invariably been low. r

A method for the preparation of butadiene-1,3 distinct from previously known methods, has been suggested by Perkin J. Soc. Chem. Ind, 31, 618 (1912). This method depends upon thereaction of n-butyl alcohol with dry hydrogen chloride to form nebutyl chloride which is then reacted with 'chlorine to give a mixture of dichlorobutanes. The dichlorobutanes are passed over soda lime at elevated temperature, yielding up their chlorine content by mission of hydrogen chloride molecules, the final product being butadiene.

The present invention deals in particular with an improvement over Perkins process of preparing butadiene-1,3. This application is a continuation-in-part of an application filed October 21, 1931, and givenserial No. 570,152 which has matured into Patent 2,038,593, April 28, 1936.

It is an object of this invention to prepare butadiene-1,3 and its homologues. A further object of the invention is to describe an improved method for preparing butadiene-1,3. Other ob-' jects will appear hereinafter.

In preparing butadiene-1,3 in accordance with the present invention, n-butyl alcohol was converted into n-butyl chloride according to the methodof Norris, Organic Syntheses'Vol. 5, p. 27 (1925), by heating the alcohol with concentrated hydrochloric acid and anhydrous zinc chloride. The pure chloride was then further chlorinated to the dichloride by reacting with chlorine. The chlorinated reaction mixture was then distilled through a. iractionating column and 'chlorine'pontent of the distillate collected in separate fractions. From the distillation temperature of the fractions collected it appears'that the chlorinated product consisted of a mixture of some unreacted butyl chloride and the 1,2-, 1,3-, and ,1,4-d10h101'0b1lltanes (possibly also some 1,1-dichlorobutane). Each of the fractions of the dichlorobutanes was distilled over coarse soda lime contained in an 1 iron tube heated to a temperature of about 700- 730 C. The volatile products coming from the tube were passed through several condensers and wash bottles and finally absorbed in chloroform or ligroin, the reaction product comprising butadime-1,3 which was formed by removal of the the dichlorobutanes in the form oi. hydrogen chloride.

The following example illustrates our mode of preparting butadiene according to this invention:

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Example 1 20 Two liters of n-b'utyl chloride, prepared from n-b'utyl alcohol according to the method of Norris (supra) were introduced into a 3 liter roundbott gmed ilask supported over an electric heating plate, the flask being provided with a thermoineter adapted to be partially immersed in the liquid. The flask was provided with a vertical glass vapor tube surmounted by a reflux condenser, the vapor tube andreflux condenser comprising a continuous passage for the vapors generated by the butyl chloride contained in the round-bottomed flask. The vapor tube was provided with a passage for introducing chlorine into the vapor space, and was subjected to light emit- 30 ted from a 1000 watt lamp placed in close proximity to the. vapor tube. I Thebutyl chloride was heated to boiling and when the butyl chloride vapors filled the vapor tube, chlorine was passed into the vapor tube, and the 1000 watt lamp turned on. The chlorin was passed in at a rate of about 1120 cc. per minute. At the beginning of the chlorination the temperature was 77 0., the boiling point of butyl chloride. As'the distillation proceeded the temperature of the liquid'rose, and

the chlori ation was allowed to proceed until the temperat reached C. This required about 6 hours. If the temperature had been allowed to go much higher than 115 6., some more highly Qhlorinatedaproducts would have been formed.

After the reaction was completed, the chlorinated diene.

V llutadiene tet- 0b mixture was roughly fractionated through a column one meter long filled with glass beads. The results of 4 runs carried on under the conditions described above are recorded in Table I.

TABLE I Chlorination expefiinents on butylehloride -120 -130" -140" -150 ISO- Grams 330 Grams 503 472 The different fractions of dichlorobutane were now separately distilled over heated soda lime. The dichlorobutane fractions were passed in the form of vapors into a steel tube containing 450 g. of coarse soda lime, the tube being heated to about'700-730 C. by means of an electric furnace. The vapors passing out of the tube traveled in succession through cooling vessels to remove "water, unreacted dichlorobutane and tarry and resinous products from the reacted mixture, the resulting vapors being substantially pure buta- A number of runs under the conditions enumerated above were madewith the different fractions of dichlorobutane to determine the yield of butadiene-1,3 obtained in each of the fractions. The butadiene formed was collected as the tetrabromide by bubbling the formed butadiene vapors through chloroform containing an excess of bromine. Complete bromination of the butadiene-1,3 caused the formation of two stereo-v isomeric tetrabromobutanes, one liquid and one solid and crystalline. The percentage yields of butadiene from the dichlorobutanes are calculated from the amount of tetrabromide obtained.

The yields of butadiene-1,3 obtained from 200 g.-

of each of the chlorinated fractions of Table I are listed in Table II, each run being about one hour in duration: I

' TABLE II Percentage of butadiene obtained from each of the chlorinated fractions 75-11o 110-120 120-130" lac-14o" 14o-15o 15940? Grams Grams Grams Grains Gram rabromlde 40 118 148 174 104 144 174 Percent Percent Percent 18.8 24.8 29.6

teinod 41 Yield of buta- Percent disne 6.9

From the data; given in Table II it is noted that the dichloro-1,3-butane fraction gave the best yield of butadiene, 29.6% of the theoretical.

Grams Percent I While the. above description of the invention is very specific it will be understood that the invention is not to be limitedto the exact conditions of the example. The soda lime used in the above example to remove hydrogen chloride from the dichlorobutanes may be replaced by any agent which will split off hydrogen .chloride from the dichlorobutanes to form butadiene. This agent will preferably be alkaline in nature. Examples of such compounds are soda lime, sodium hydroxide, potassium hydroxide, potassium carbonate, etc. varied from that given in the example It is necessary that the temperature b'eelevated and it is preferable that it be in the neighborhood of 730 C. Some variation from this latter range is, however, permissible.

A preferred method for carrying out the proc-.

- ess of the present invention involves flash distillation. Good yields of butadiene are obtained by flash distilling the various dichlorobutanes in contact with soda lime.

The butadiene produced by the process of this reaction is useful as a starting material in the synthesis of a wide variety of both old and new compounds. It has been found particularly advantageous in the production of chlorine substituted hydrocarbons.

The process of the present invention has various distinct advantages over the process previously described for the production of butadiene. Among these may be mentioned the fact that a pure product is obtained more readily and in much larger yield.

" It is apparent that many widely different em- The temperature may, likewise, be

bodiments of this invention may be made without departing from the spirit and scope thereof and, therefore, it is not to be limited except as indicated in the appended claims.

I claim: v

1. A process for preparing butadiene which comprises reacting n-butyl chloride with chlorine, separating" from the reaction mixture fractions, each of which contains an isomeric dichlorobutane, then passing separate fractions, at a temperature of about 700 to 730 C. over an alkaline agent which will split off hydrogen chloride from the dichlorobutane to form butadiene.

2. In the process of preparing butadiene, the step which comprises passing a dichlorobutane of the group consisting of 1,2-dichlorobutane, 1,3-dichlorobutane and 1,4-dichlorobutane over an alkaline agent which will split off hydrogen chloride from the dichlorobutane to form butadiene', at a temperature of about 700 to 730 C.

- 3. The process of claim 2 in which the agent.

is soda lime.

4. In the process of preparing butadiene, the

. step which comprises contacting 1,3-dichlorobutane at a temperature of about 700 to 730 C. with an alkaline agent which will split ofi hydrogen I chloride from the dichlorobutane to form butadiene.

5. The process of .claim 4 in which the agent is soda lime..

6. The process of claim 4 which the dichloro-,

butane is flash distilled in contact with the alkaline agent. f I

7. The process of claim 1 in which the agent is soda lime.

IRVING E. MUSKAT. 

